Submission #7870169

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Source Code Expand

// template version 1.12
using namespace std;
#include <iostream>
#include <bits/stdc++.h>

// varibable settings
#define infile "../test/sample-1.in"
#define int long long //{{{
const int INF=1e18;
const int MOD=1e9+7; //}}}

// define basic macro {{{
#define _overload3(_1,_2,_3,name,...) name
#define _rep(i,n) repi(i,0,n)
#define repi(i,a,b) for(int i=(int)(a);i<(int)(b);++i)
#define rep(...) _overload3(__VA_ARGS__,repi,_rep,)(__VA_ARGS__)
#define _rrep(i,n) rrepi(i,0,n)
#define rrepi(i,a,b) for(int i=(int)((b)-1);i>=(int)(a);--i)
#define rrep(...) _overload3(__VA_ARGS__,rrepi,_rrep,)(__VA_ARGS__)
#define each(i,a) for (auto&& i : a)
#define all(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
#define pb(a) push_back(a)
#define mp(a, b) make_pair(a, b)
#define ceil(a,b) ((a)+(b)-1)/(b)
#define uni(x) sort(all(x));x.erase(unique(all(x)),x.end())
#define ub upper_bound
#define lb lower_bound
#define posl(A, x) (lower_bound(all(A), x)-A.begin())
#define posu(A, x) (upper_bound(all(A),x)-A.begin())
template<class T> inline void chmax(T &a, const T &b) { if((a) < (b)) (a) = (b); }
template<class T> inline void chmin(T &a, const T &b) { if((a) > (b)) (a) = (b); }

typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef long double ld;
typedef pair<int,int> pii;
typedef tuple<int,int,int> iii;

template<typename T> using PQ = priority_queue<T, vector<T>, greater<T>>;
struct Fast { Fast(){ std::cin.tie(0); ios::sync_with_stdio(false); } } fast;

#if defined(PCM) || defined(LOCAL)
  #include "lib/dump.hpp"
#else
  #define dump(...) 42
  #define dump_1d(...) 42
  #define dump_2d(...) 42
#endif
//}}}

int solve(){
  int n;cin>>n;
  vvi G(n);
  rep(i,n){
    string s;cin>>s;
    rep(j, i+1, n){
      if (s[j]=='1') {
        G[i].pb(j);
        G[j].pb(i);
      }
    }
  }
  dump(G);

  int ans = -1;
  rep(sv, n){
    stack<int> st;
    int k = 1;
    st.push(sv);
    bool valid = true;
    vi level(n, -1);
    level[sv] = 1;

    while(true){
      k++;
      dump(sv, k);

      stack<int> nst;
      while(!st.empty()){
        int v = st.top();st.pop();
        each(to, G[v]){
          if (level[to]==-1){
            nst.push(to);
            level[to] = k;
          }
          else if (level[to]==k or level[to]==k-2){
          }
          else{
            dump(to, k, level[to], level);
            valid = false;
          }
        }
      }
      if (!valid) break;

      if (nst.empty()) break;
      else{
        st = nst;
      }
    }
    dump(level);
    // rep(i,n){
    //   each(j, G[i]){
    //     if (level[i]-level[j]!=1 and level[i]-level[j]!=-1)
    //       valid = false;
    //   }
    // }
    if (valid) chmax(ans, k-1);
  }
  cout << ans << endl;

  return 0;
}

signed main() { //{{{
#ifdef INPUT_FROM_FILE
  std::ifstream in(infile);
  std::cin.rdbuf(in.rdbuf());
#endif
  solve();
  return 0;
} //}}}

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